1. Technical Field
The present invention relates to an optical diaphragm and a projector.
2. Related Art
There has been employed in a camera a light-shielding device capable of changing an aperture area formed on an optical axis by a plurality of light-shielding vanes that are movable in a plane orthogonal to the optical axis (see, for instance, Document: JP-A-9-189935).
In the light-shielding device disclosed in the Document, the plurality of light-shielding vanes include first vanes that are each made of only a resin material and second vanes that each include at least a portion made of a metal material, the first and second vanes being arranged alternately in an optical axis direction. The second vanes each have a projected portion abutting and sliding on the first vanes or a supporter. With such arrangement, a defect in operational characteristics associated with abutting and sliding of the plurality of vanes can be improved.
However, when the light-shielding device disclosed in the Document is installed in a projector and used as an optical diaphragm for adjusting a light quantity of a light beam irradiated by a light source device, the following problem will arise.
When the light beam irradiated by the light source device is intercepted by the light-shielding vanes, a temperature of the light-shielding vanes is known to rise to 200° C. or higher. However, the first light-shielding vanes are made of a resin material in the light-shielding device disclosed in the Document, so that the first light-shielding vanes cannot cope with such temperature rise caused by the light interception.
Here, in order to solve the problem described above, it is conceived to form the plurality of light-shielding vanes by a metal material that enables the light-shielding vanes to cope with the temperature rise caused by the light-interception. However, such arrangement generates a frictional noise due to abutting and sliding of the plurality of light-shielding vanes, thus being unable to ensure silence of the device.